(a) Field of the Invention
The present invention relates to a liquid detersive bleaching composition comprising sodium hypochlorite as the active bleaching ingredient, which composition is superior in bleaching efficiency, detergency, foaming efficiency and penetration into fabric.
(B) Description of the Prior Art
Sodium hypochlorite has been known for a long time as a chemical having various effects such as disinfection, sterilization and bleaching. However, in the case of sodium hypochlorite prepared by the normal method, if it is not subjected to a particular purification, its aqueous solution tends to contain inorganic salt in an amount of about 0.5 to 1.5 times of the available amount of chlorine and at the same time a very small amount of heavy metal ion of, for instance, Ni, Cu, Co, etc. which are said to promote the decomposition of sodium hypochlorite. Accordingly, even when left standing, sodium hypochlorite would gradually decompose and the bleaching efficiency thereof would deteriorate, so that it is deficient in practicality. In order to make up for such defects, alkaline substances such as caustic soda have hitherto been added thereby to keep a certain degree of stability.
Further, as a means for enhancing the penetrating of sodium hypochlorite into fiber, fabric and the like and promoting the bleaching efficiency thereof, various processes of adding some surface active agent to sodium hypochlorite-based bleaching compositions have been proposed. However, inasmuch as the rate of decomposition of sodium hypochlorite is generally accelerated by the presence of organic substances in its solution, addition of surface active agents which are common detergent ingredients, such as anionic surface active agents like linear alkylbenzene sulfonate, alkyl sulfate, etc. and nonionic surface active agents like polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, etc., accelerates decomposition of sodium hypochlorite. Thus, we could not obtain a stable liquid detergent bleaching composition superior in bleaching power.
Therefore, as an alternative, there has been proposed application of such surface active agents that have less effect on the stability of hypochlorite even when mixed therewith. For instance, the Japanese Patent Publication No. 6268/1963 has a description about the effect that alkyl diphenyl ether disulfonate stabilizes sodium hypochlorite. However, there is no detailed description as to the degree of stabilization, and as a matter of fact, in the case of employment of an unrefined sodium hypochlorite, there is observed more deterioration of stability and increase in the rate of decomposition of sodium hypochlorite than in the case where no alkyl diphenyl ether disulfonate is added. Further, the Japanese Patent Publication No. 2103/1968 and Japanese Patent Publication No. 1086/1973 have descriptions to the effect that polyoxyethylene alkylphenyl ether sulfate can stably coexist with sodium hypochlorite in an aqueous solution. However, even in this case, the rate of decomposition of sodium hypochlorite is rather enhanced as compared with that in the case where no polyoxyethylene alkylphenyl ether sulfate is added. In other words, none of the known surface active agents which have been said to be able to coexist stably with sodium hypochlorite can prevent the decomposition of sodium hypochlorite; they are merely less active in accelerating the decomposition of sodium hypochlorite.